Computers can use file systems to store different types of objects. Typical objects include files and directories. Directories are hierarchical arrangements of objects, and may have nested objects. Directories include files or file folders and sub-directories. File systems use storage media to store objects, such as hard drives, flash media, or other non-volatile storage.
A file system also uses and stores metadata that describes information about the file system. Such metadata is typically hidden from users (which can include applications in a computer system). The metadata describes where on the physical storage media the files are located. The storage media may be considered as a large array of bytes. However, the file system does not appear to a user or to be an array of bytes, but rather includes a hierarchy of objects such as files and directories. The mapping between the bytes in the storage media and the hierarchy of the files is described in the metadata. In other words, the metadata provides a mapping between the physical storage of the data and how the data is presented to the user. More specifically, the metadata provides a description as to where each file or portion of a file is located on the storage media. Note that while a file or directory may appear contiguous to a user, the file as stored on the storage media may be located in many different areas.